Biomedical subjects
Publications and source records attributed to S E Jørgensen.
The radical variability of ecosystems such as lakes when reacting to prevailing conditions has in many situations found traditional modelling too inflexible. The introduction of eco-exergy, a measure of a system's distance from thermodynamic equilibrium, has enabled models to deal with ecosystems that can show major structural changes resulting from adaptation and shifts in species composition.
This paper presents an overview of the application of models on aquatic ecosystems. More than 17% of the models published in the focal journal in the field, Ecological Modelling, are aquatic ecosystem models. An increasing number of papers are dealing with the theoretical aspects of modeling--new modeling approaches and techniques, how models can be used to reveal ecosystem properties, and how models can better reflect the properties of ecosystems. This development implies that today we have more types of models. The characteristics, the advantages, and the disadvantages of these model types are presented briefly. The selection criteria for the presented model types are discussed, and the application of these types to models for aquatic ecosystems is reviewed. A recent improvement in model calibration of particular interest for aquatic ecosystems is presented, and the perspectives resulting from this new calibration procedure and from possible hybrids of the presented model types are discussed.
It is the intention of this paper to demonstrate that environmental technology must be supplemented by other tools to be able to solve environmental problems properly. Five cases are used to illustrate the possibilities of ecological engineering, a new engineering field based on ecology, as chemical engineering is based on chemistry. It encompasses restoration of ecosystems, utilization of ecosystems to the benefit of both mankind and nature, construction of ecosystems, and ecologically sound planning of ecosystems from a holistic point of view. Ecological engineering requires a good knowledge of the system properties of ecosystems to be able to fully utilize the possibilities that ecosystem management offers. Models reflecting the ecosystem properties are furthermore needed to be able to quantify the effects of the ecological engineering solutions to the environmental problems. This is clearly demonstrated in two of the five case studies presented in the paper.
Algal toxicity of antibacterial agents applied in fish farming was investigated. The growth-inhibiting effects of amoxicillin (A), flumequine (F), oxolinic acid (OA), oxytetracycline hydrochloride (OT), sarafloxacin hydrochloride (SF), sulfadiazine (SD), and trimethoprim (T) were investigated by a modified test procedure based on the procedure described in the ISO 8692 (1989) protocol on three algal species: the freshwater cyanobacteria Microcystis aeruginosa, the freshwater green alga Selenastrum capricornutum, and the marine cryptophycean Rhodomonas salina. Algal growth was measured as increased chlorophyll concentration by extraction with ethanol followed by measurement of fluorescence. Results were quantified in terms of growth rates using the Weibull equation to describe the concentration response relationship. M. aeruginosa showed higher sensitivity compared to both R. salina and S. capricornutum, whereas the results for the latter two were more or less identical. The toxicity (EC50 value, mg/L) in decreasing order were A (0.0037), SF (0.015), SD (0.135), F (0.159), OA (0.180), OT (0.207), and T (112) for M. aeruginosa; OT (1.6), OA (10), T (16), F (18), SF (24), SD (403), and A (3108) for R. salina; and OT (4.5), F (5.0), SD (7.8), OA (16), SF (16), T (130), and A (NOEC > 250) for S. capricornutum. Applying this test procedure the toxicity of antibacterial agents, being mono- or polyprotic compounds, may be underestimated because of partitioning between ionized and unionized forms.
The paper outlines the history of modelling and presents a status of ecological modelling: what is the modelling effort of various ecosystem and various environmental problems. Typical validation results and prognosis validation results of a eutrophication model are applied as an illustration of what models can do in environmental management. Structural dynamic modelling which considers parameters that are changed currently by optimisation of a so-called goal function is presented as one of the recent development to overcome one of the most crucial problems in modelling, namely to consider adaptation. Two case studies are presented to illustrate this approach, namely application of biomanipulation and eutrophication of a shallow lake. Forecast on the directions of development is finally presented.
Medical substances (pharmaceuticals) are a group of substances that until recently have been exposed to the environment with very little attention. The reason why they may be interesting as environmental micropollutants, is that medical substances are developed with the intention of performing a biological effect. Especially antibiotics used as growth promoters, as feed additives in fish farms are anticipated to end up in the environment. Very little is known about the exposure routes of the medical substances to the environment. Only few investigations have reported findings of medical substances in other field samples than sediment or treated waste water samples. Several substances seem to be persistent in the environment. This paper outlines the different anticipated exposure routes to the environment, summarises the legislation on the subject and gives an outline of present knowledge of occurrence, fate and effect on both the aquatic and terrestrial environments of medical substances. Present knowledge does not reveal if regular therapeutic use may be the source of a substance carried by sewage effluent into the aquatic system, even though clofibrate, a lipid lowering agent, has been identified in ground and tap water samples from Berlin. Further research would be necessary to assess the environmental risk involved in exposing medical substances and metabolites to the environment.
The relevance of a positive chromium patch test in females with hand eczema is very often obscure. In order to investigate the exposure to chromium in an everyday event as cleaning, the chromium content of water samples from various steps of the cleaning process in a Danish hospital was analyzed. During cleaning the chromium contamination increased above the theoretical limit necessary for sensitization. House dust contains considerable amounts of chromium, and will readily liberate it into suspension. All the chromium was found in the trivalent form.
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